Rotary joints are used in particular in trucks and tractors that travel over different surfaces, in order to adapt the tire pressure to the road surface characteristics. It is advantageous in fields or on unpaved streets when a tire pressure is low, in order to increase the traction of the vehicle. On paved streets a higher tire pressure is preferred, in order reduce tire wear and fuel consumption. The rotary joint makes it possible to vary the tire pressure by increasing or decreasing the air pressure in a pressure chamber.
DE 10 2012 222 339 A1 discloses a fluid rotary joint for sealing a fluid pressure chamber between a rotatable shaft and a shaft receiver. The fluid rotary joint comprises a seal carrier and a fitted body, wherein the seal carrier is non-rotatably connected in a fluid-tight manner to the shaft or the receiver, and the fitted body bears in a fluid-tight manner on receiver or the shaft. The fitted body and the seal carrier are disposed at least in sections at a spacing to one another, in order to form a fluid-tight space between them. Furthermore, two sealing rings, spaced axially apart from one another, are provided, each of which bear in a sealing manner with a bearing surface against the seal carrier and with a bearing surface against the fitted body, in order to seal the fluid pressure chamber to the exterior at both ends, which can each rotate, preferably independently of one another, in relation to the seal carrier and/or the fitted body. The seal carrier and the fitted body collectively form two receiving grooves for the sealing rings, axially spaced apart from one another, wherein the receiving grooves are open toward the fluid pressure chamber, and each comprise at least one retention projection, which secures the sealing ring disposed in the receiving groove, at least in sections, against a radial displacement from the groove toward the fluid pressure chamber.
In other words, the respective sealing ring is provided for both a radial and an axial seal. With a pressure buildup in the pressure chamber, the respective sealing ring bears axially on a sealing surface. The axial pressure exerted by the respective sealing ring against the sealing surface is relatively high, such that due to an increased wear as well as an increased thermal load, the service life of the respective seal is significantly reduced. With very high pressures, the respective seal may even fail immediately.